Signal protection

ABSTRACT

A signal protector utilizes a variable latency station to provide error correction.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.15/626,471 filed Jun. 19, 2017 entitled SIGNAL PROTECTION which is acontinuation of U.S. patent application Ser. No. 14/923,317 filed Oct.26, 2015, now U.S. Pat. No. 9,684,572, which is a continuation of U.S.patent application Ser. No. 13/855,961 filed Apr. 3, 2013 now U.S. Pat.No. 9,172,507 which claims the benefit of U.S. Prov. Pat. App. No.61/619,907 filed Apr. 3, 2012 entitled DYNAMIC BUFFER SIGNAL PROTECTIONand U.S. Prov. Pat. App. No. 61/625,063 filed Apr. 16, 2012 entitledSIGNAL PROTECTION.

BACKGROUND OF THE INVENTION

Known signal protection schemes include error correction using multiplechannels and/or large static buffers. Such systems utilize excessivebandwidth and/or introduce relatively long latency. Although signalprotection innovations are not a focus area of the telecommunicationsindustry, improvements that are adopted by the industry have thepotential to benefit large groups of consumers.

FIELD OF INVENTION

This invention relates to the electrical arts. In particular, a signalis protected through the use of a dynamic buffer.

DISCUSSION OF THE RELATED ART

Some signal protection systems are known. For example, some signalprotection systems using dual paths that allow for switching between afailed/failing path and an alternate path are known. These dual pathsystems consume identical bandwidth on two paths because both pathscarry the active feed; one path provides a main signal and one pathprovides an identical standby signal. Further, some forward errorcorrection schemes are known. Their development has not generally been afocus area of the telecommunications industry, perhaps due to the use ofthe dual path protection systems mentioned above. But, known systemsgenerally suffer from one or more of hardware complexity, softwarecomplexity, high initial cost, high operating costs, large additions torequired bandwidth, and signal degradation. Selected embodiments of thepresent invention provide solutions to one or more of these problems.

SUMMARY OF THE INVENTION

The present invention provides a signal protector. Embodiments utilize avariable latency station. In various embodiments, a signal protectorallows one or more of transparent, seamless, and uninterruptedprotection of a feed across a dual network while consuming bandwidth ona single connection at any point in time. And, in various embodiments, asignal protector allows one or more of transparent, seamless, anduninterrupted protection of a feed across a dual network while consumingbandwidth principally on a single connection.

In an embodiment, the invention provides means and methods fortransparent and/or seamless protection of a feed across a dual networkwhile limiting bandwidth consumption to a single connection while thereare no communications errors.

And, in an embodiment, a signal protector comprises: first and secondbuffers in signal communication via path A and path B; the buffershaving first and second buffer lengths (seconds of data); the first andsecond buffer lengths being a function of two times the path time of thelonger of paths A and B; the signal protector operative to use one ofthe paths before there is a signal loss event on that path; the signalprotector operative to use the other of the paths after the signal loss;and, the buffer sizes being selected to allow for seamless datathroughput.

In an embodiment, a data protection method comprises the steps of:providing data path A and data path B; each of the data paths extendingbetween first and second stations; the first station providing data topath A; the second station receiving data initially from data path A;and, providing an uninterrupted second station output following a datafault via utilizing a buffer of the second station to maintain anunfaulted second station output after the data fault is detected, thefirst station providing data to data path B, the data including resenddata from a first station buffer, the resend data including the faulteddata, and the data from data path B bypassing at least a portion of thesecond station buffer to merge the resent data with the data remainingin the second station buffer.

Some embodiments further comprise the steps of: sizing the buffer of thesecond station such that the time required for a bit to traverse thesecond station buffer equals or exceeds t; where t=t1+t2; where t1equals the time required for one bit of data to traverse path A; and,where t2 equals the time required for one bit of data to traverse pathB.

Some embodiments further comprise the steps of: sizing the buffer of thefirst station such that the time required for a bit to traverse thefirst station buffer equals or exceeds t.

Some embodiments further comprise the steps of: sizing the buffer of thesecond station such that the time required for a bit to traverse thesecond station buffer equals or exceeds t+r1+r2+r3; where t=t1+t2; wheret1 equals the time required for one bit of data to traverse path A;where t2 equals the time required for one bit of data to traverse pathB; where r1 equals the time required by the second station to detect thefault; where r2 equals the time required by the first station to respondto a received request to resend data including data replacing the faultydata; and, where r3 equals the time required by the second station tomerge resent data with data remaining in the second station buffer.

Some embodiments further comprise the steps of sizing the buffer of thefirst station such that the time required for one bit of data totraverse the first station buffer equals or exceeds t+r1+r2.

Some embodiments further comprise the step of the second station sendinga request to resend data replacing the faulty data and the first stationreceiving the request during a time period substantially equal to t1.

Some embodiments further comprise the step of the first stationbeginning to send resend data and the second station beginning toreceive resend data during a time period substantially equal to t2.

Some embodiments further comprise the step of rebuilding the secondstation buffer wherein rebuild operations include operating path B at adata rate higher than a nominal data rate for path B, utilizing some ofthe path B data to maintain a second station buffer output at itsnominal data rate, utilizing some of the path B data to rebuild thesecond station buffer, and returning the path B data rate to its nominaldata rate after the second station buffer has been rebuilt.

Some embodiments further comprise the step of the second station relyingon path B to maintain the second station buffer.

Some embodiments further comprise the step of relying on path A torebuild and maintain the second station buffer following a transmissionfault detected while path B is active.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described with reference to the accompanyingfigures. The figures, incorporated herein and forming part of thespecification, illustrate the present invention and, together with thedescription, further serve to explain the principles of the inventionand to enable a person skilled in the relevant art to make and use theinvention.

FIG. 1 a protection system in accordance with the present invention.

FIG. 2 shows exemplary operation of the protection system of FIG. 1.

FIG. 3 shows another embodiment of the protection system of FIG. 1.

FIG. 4 shows exemplary operation of the protection system of FIG. 3.

FIG. 5 shows exemplary operation of the protection system of FIG. 4.

FIG. 6 shows another embodiment of the protection system of FIG. 1.

FIG. 7 shows an exemplary timing diagram of the protection system ofFIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The disclosure provided in the following pages describes examples ofsome embodiments of the invention. The designs, figures, anddescriptions are non-limiting examples of certain embodiments of theinvention. For example, other embodiments of the disclosed device may ormay not include the features described herein. Moreover, disclosedadvantages and benefits may apply to only certain embodiments of theinvention and should not be used to limit the disclosed inventions.

Where parts are connected, descriptions herein include the term“coupled” which refers to either direct or indirect connections. Directconnections provide for a first part connected directly to a secondpart, for example A connected directly to B. Indirect connectionsprovide for a first part connected indirectly to a second part, forexample A connected indirectly to C via B.

FIG. 1 shows a signal protection system in accordance with the presentinvention 100. A variable latency station “VLS” 108 and a source of data102 are in signal communications via communications paths A 104 and B106. In various embodiments, the VLS is operable to correct faulty databefore it reaches a VLS output 110.

FIG. 2 shows an exemplary operation of the signal protection system ofFIG. 1 200. A VLS for receiving data and for outputting data is provided204. VLS data output is initially supported via a first data path, suchas Path A, that transports data to the station 208. After a data faultis detected, such as a fault detected in the VLS, unfaulted correctivedata is transported to the VLS via a second data path, such as Path B212. Error correction with uninterrupted VLS data output includesreducing VLS latency, for example bypassing at least a portion of a VLSbuffer, and switching VLS data output support from the first path to thesecond path 216.

FIG. 3 shows a signal protection system embodiment with transmit andreceive buffers 300. An encoder 302 with a data input 340 and a decoder322 with a data output are in signal communications via communicationspaths A 312 and B 314. As is further described below, decoder variablelatency enables correction of faulty data before it reaches the decoderoutput.

The encoder 302 incorporates a transmit buffer 304 for receiving datafrom a transmit buffer data input 340 and a transmitter 306 fortransmitting transmit buffer data to the decoder 322. In variousembodiments, the transmitter includes a Path A transmitter 308 and aPath B transmitter 310 coupled between transmit buffer outputs 307, 309and respective data paths Path A and Path B.

The decoder 322 incorporates a receiver 326 coupled between Paths A andB and a receive buffer 324. The receive buffer is coupled to a decoderdata output 342. In various embodiments, the receiver includes a Path Areceiver 328 and a Path B receiver 330 coupled between receiver bufferinputs 329, 331 and respective data paths Path A and Path B.

FIG. 4 shows exemplary operation of the signal protection system of FIG.3 400. An encoder and a decoder are provided with data paths A and Btherebetween 402. Initially, a data stream is transported from theencoder to the decoder over Path A to support decoder data output 404.After a data fault, unfaulted data in the decoder buffer is used tosupport uninterrupted decoder data output 406. Correction includestransporting corrective data and rebuilding the data stream in thedecoder. Corrective data stored in the encoder transmit buffer istransported to the decoder 408. An uninterrupted data stream isrecreated from data including corrective data and new data transportedover Path B 410. Transport of new data over Path B continues andmaintains uninterrupted decoder data output 420.

FIG. 5 shows another example of operation of the signal protectionsystem of FIG. 3 500. An encoder and a decoder are provided with datapaths A and B therebetween 502. Initially, a data stream is transportedfrom the encoder to the decoder over Path A to support decoder dataoutput 504. After a data fault, unfaulted data in the decoder buffer isused to support uninterrupted decoder data output 506. Correctionincludes transporting corrective data and rebuilding the data stream inthe decoder. Corrective data stored in the encoder transmit buffer istransported to the decoder 508. An uninterrupted data stream isrecreated from data including corrective data and new data transportedover Path B 510. Transport of new data over Path B continues andmaintains uninterrupted decoder data output 520.

Recreation of the uninterrupted data stream 510 includes: receiving PathB corrective data at the decoder and bypassing some part of the receivebuffer to eliminate gap between corrective data and unfaulted data 512;receiving Path A simultaneous data arriving at the decodersimultaneously with corrective data and merging this data with thecorrective data 514; and, receiving new Path B data arriving at thedecoder and merging this data with the simultaneous data 516.

Persons of ordinary skill in the art will recognize the decoder receivebuffer 324 is not filled after the correction process described above.The buffer can be refilled by increasing the data rate between theencoder and the decoder such that it exceeds the data rate required tosupport the decoder output. For example, the data rate of Path B can beincreased, Paths A and B can be used simultaneously, or both of thesetechniques can be used.

FIG. 6 shows a signal protection system embodiment with return controlpaths A and B 600. A transmit buffer 604 with an incoming feed 602 and areceive buffer 614 with an output 616 are in signal communication viaNetwork Paths A 606 and B 612. Each of the network paths has acorresponding return control path 608, 610.

The transmit buffer 604 includes pre and post launch buffering 634, 636.The pre-launch buffering receives an incoming feed 602 and supports amain stream output 640. The post-launch buffering 636 maintains acorrective copy of launched data that is transported as a protectionstream 638. In the event of a data fault, a data path other than themain network data path is used to transport the protection stream. Forexample, transport of the main stream over Network Path A immediatelyprior to a data fault would result in transport of the protective streamover Network Path B immediately after the data fault.

The receive buffer 614 includes receive buffering 654 and protectionmerge 656. Main stream data 660 is delivered to the receive bufferingand protection data 658 is delivered to the protection merge. When thereis no data fault, the receive buffering data is not manipulated by theprotection merge and the data is delivered to the receive buffer output616. Alternatively, a data error results in operation of the protectionmerge which merges unfaulted data from the receive buffering with theprotective stream 638.

In an exemplary operating mode, buffer sizing is illustrated.

-   -   a. For example, the path time ‘t’ is approximately 10 ms which        is equivalent to approximately 2,000 km (and therefore a return        trip time is ˜20 ms). (t is the value of the longest of the 2        paths). ‘r’ is a value that allows for response times at each        end plus a small margin—typically 5 ms    -   b. A keep-alive ‘OAM’ packet flow is maintained on both        paths—sending approximately 1 packet-per-second (on same IP        address as media flow but different port number) from the        encoder to decoder    -   c. The round trip time is continually monitored with the use of        a return packet OAM from decoder to encoder    -   d. Encoder sends actual traffic on only path A (for example)    -   e. Encoder fills transmit buffer to a level of 3t (30 ms)—this        is r (5 ms) pre-send and 2t+r (25 ms) post-send (i.e., the        transmit buffer always contains the last 25 ms of data already        transmitted) (this value is varied according to the measured        round-trip time)    -   f. Upon receiving the stream, the decoder fills receive buffer        to 2t+r (25 ms) before starting to output i.e. there is a 25 ms        worth of data held in output buffer    -   g. If the path A signal is lost at the decoder, the decoder        signals to the encoder to indicate a lost feed Time taken=loss        detection time plus t (10 ms). The decoder continues to output        data from its buffer    -   h. At this point the encoder commences transmission of the feed        on path B, but from the end of the buffer—i.e., it is        re-transmitting the last 25 ms that has already been sent    -   i. Upon receipt of the stream on the B feed, the decoder takes        this stream (discarding any duplicate packets) to maintain a        continual output flow    -   j. Once this process is complete, the decoder indicates to the        encoder the amount of buffer fill it currently now has and how        much it needs to be re-filled to be ready for another protection        event    -   k. The encoder then enters a ‘nominal bit rate plus a bit’        transmission period to get the decoder buffer back to normal        operating point (the alternative technique that could be used        here is two also use path A when it recovers—i.e. both paths in        use for a fraction of a second)    -   l. Once the OAM on path A indicates it has been restored, the        system is ready to protect again, the other way

As persons of ordinary skill in the art will appreciate, round-trip pathlength is approximated above as two times the length of the longer path.Where the paths are of substantially different lengths, the round-trippath length can be more accurately represented as t1 and t2. Similarly,encoder/decoder reaction times can be represented as the time to detecta fault in the encoder r1, the time for the encoder to assemble andlaunch a message requesting corrective data from the decoder r2, and thetime for the decoder to interpret this message and launch the correctivedata r3.

FIG. 7 shows a timing table illustrative of an exemplary operating modeof the protection system of FIG. 6 700.

-   -   a. At index 1, the protection system is sending via Path A    -   b. At index 2, the protection system is sending via Path A,        discovers an error and requests a resend (r1)    -   c. At index 3, the protection system is sending via Path A and        the resend message is being transported over Network Path A        return (t1)    -   d. At index 4, the protection system is sending over path A and        the protection system receives the resend request and prepares        to resend (r2)    -   e. At index 5, the protection system is sending over path A and        the protection system is sending the post-launch/corrective data        over path B (t2)    -   f. At index 6, the protection system begins to receive the        corrective data and begins merging data to maintain an        uninterrupted output (r3)    -   g. At index 7, the protection system is sending data over Path B

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. It will be apparent to those skilledin the art that various changes in the form and details can be madewithout departing from the spirit and scope of the invention. As such,the breadth and scope of the present invention should not be limited bythe above-described exemplary embodiments, but should be defined only inaccordance with the following claims and equivalents thereof.

What is claimed is:
 1. A data protection method comprising the steps of:providing an encoder including a transmit buffer between an encoderinput and each of a path A transmitter and a path B transmitter;providing a decoder including a receive buffer between a decoder outputand each of a path A receiver and a path B receiver; and,interconnecting data paths A and B between the encoder and the decoder.2. The data protection method of claim 1 further comprising the stepsof: transporting a data stream from the encoder to the decoder over pathA to supply a decoder data output; after a data fault, using unfaulteddata in a decoder buffer to continue decoder data output withoutinterruption; transporting corrective data stored in an encoder transmitbuffer to the decoder via path B; and, continuing an uninterruptedsupply of data to the decoder data output using the corrective data andthe encoder data stream transported over path B.
 3. The data protectionmethod of claim 2 wherein data path B does not redundantly propagate thesame data values as data path A.
 4. The data protection method of claim3 wherein bandwidth consumption is limited to a single connection whilethere are no communications errors.
 5. The data protection method ofclaim 1 further comprising the steps of: transporting data over path Abut not over path B during a pre-fault operating mode; transporting dataover path B but not over path A during a fault recovery operating mode;transporting encoder data over path B but not over path A during apost-recovery operating mode; and, wherein the pre-fault, faultrecovery, and post-recovery operating modes are for providing anuninterrupted supply of data to a decoder data output.
 6. The signalprotection method of claim 5 wherein communications between the encoderand decoder buffers include path A and path B communications directed tothe decoder buffer and path A and path B return control flowcommunications directed to the encoder buffer.
 7. A signal protectiondevice comprising: an encoder including a transmit buffer between anencoder input and each of a path A transmitter and a path B transmitter;a decoder including a receive buffer between a decoder output and eachof a path A receiver and a path B receiver; data paths A and B thatextend between the encoder and the decoder; data path B does notredundantly propagate the same data values as data path A; wherein adata fault on data path A causes path B to resend the faulted data whileuninterrupted decoder output continues; an uninterrupted decoder outputis a segment of unfaulted path A data; and, the segment is ahead offaulted path A data and output from the receive buffer.
 8. The signalprotection device of claim 7 wherein bandwidth consumption is limited toa single connection while there are no data faults.